Lubricating compositions containing metal phosphonates

ABSTRACT

THE EXTREME PRESSURE PROPERTIES OF ORGANIC FLUIDS ARE IMPROVED BY ADDING THERETO A SMALL AMOUNT OF A GOLD HYDROCARBYL HYDROCARBYLPHOSPHONATE COMPLEXED WITH A BASIC NITROGEN COMPOUND OR ANOTHER METAL HYDROCARBYL HYDROCARBYLPHOSPHONATE WHICH MAY OR MAY NOT BE SO COMPLEXED.

3,798,162 LUBRICATING COMPOSITIONS CONTAINING METAL PHOSPHONATES JosephJ. Dickert, Jr., and Carleton N. Rowe, Lower Makefield Township, Pa.,assignors to Mobil Oil Corporation No Drawing. Continuation-impart ofabandoned application Ser. No. 70,901, Sept. 9, 1970. This applicationAug. 14, 1972, Ser. No. 280,604

Int. Cl. C10m 1/44, 3/38, 5/24 US. Cl. 252-32.5 15 Claims ABSTRACT OFTHE DISCLOSURE The extreme pressure properties of organic fluids areimproved by adding thereto a small amount of a gold hydrocarbylhydrocarbylphosphonate complexed with a basic nitrogen compound oranother metal hydrocarbyl hydrocarbylphosphonate which may or may not beso complexed.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of US. application Ser. No. 70,901, filed Sept. 9,1970 and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates in one of its aspects to novel lubricant compositions. Moreparticularly, it relates to such compositions containing anti-wearamounts of metal phosphonates either uncomplexed or complexed with abasic nitrogen compound. In another of its aspects, the inventionrelates to a novel method of protecting rubbing metal surfaces.

Description of the prior art The metal surfaces of machinery or enginesoperating under heavy loads wherein metal slides against metal mayundergo excessive wear or corrosion. Often the lubricants used toprotect the metal surfaces deteriorate under such heavy loads and as aresult, do not prevent wear at the points of metal to metal contact.Consequently, the performance of the machine or engine will suffer, andin aggravated cases the machine or engine may become completelyinoperative.

There have been many attempts to devise additive systems which wouldprovide satisfactory protection, but these have not always beensuccessful. The metal phosphonate additives of the present invention arebelieved capable of overcoming some of the deficiencies of prior artadditives and to provide lubricating oil compositions with enhancedanti-Wear characteristics.

US. 2,758,971 describes a class of metal phosphonates which aredisclosed as having properties which prevent breakdown of oils at hightemperatures. These additives may be described as diorganohydroxyorganophosphonates or certain metal salts thereof.

In another US. Pat. (2,792,374) are disclosed the alkali metal salts ofcertain alkyl alkylphosphouic acids as defoamants in aqueous systems.

Still another US. Pat. (2,982,727) discloses lubricating oilcompositions containing certain salts of oxygencontaining esters ofphosphorus. The esters are phosphonates similar to those described inUS. 2,758,971.

nited States Patent 0 3,798,162, Patented Mar. 19, 1974 SUMMARY OF THEINVENTION In accordance with the invention there are provided lubricantcompositions comprising a major amount of a lubricant and an amountsuflicient to impart anti-wear properties thereto of a compound of theformula:

wherein R is hydrocarbyl containing from 14 to about 30 carbon atoms, Ris hydrocarbyl containing from 1 to about 6 carbon atoms, X is a basicnitrogen-containing compound, Z is from 1 to 4, q is 0 or 1, M is ametal selected from the group consisting of Groups I-B, II-B, and IV-Aof the Periodic Table and n is the valence of M, q being 1 and n being 3when M is gold.

When used for anti-wear action, these compounds may be present in thelubricant in a concentration of from about 0.001 to about 10%,preferably from about 0.1 to about 5% by weight thereof.

DESCRIPTION OF SPECIFIC EMBODIMENTS As has already been stated, R of theabove formula contains from 1 to about 6 carbon atoms. Preferably, Rwill contain from 1 to 3 carbon atoms and more preferably R will be themethyl group. Thus, among those compounds contemplated will be thefollowing:

R R M MethyL. Cu, Au, Ag, Pb, Zn or Hg.

Do-. yl Same as above. Do- Tnacontyl.-. Do

Hexadecyl D0. yl Octadesyl. Do. Docosyl Do. Tricosyl.-- Do. TetraeosylDo.

The above and other compounds may be prepared by known means. One suchmeans involves, first, the preparation of the phosphonic acid byreacting a hydrogen phosphonate [(RO) P(O)H] and an olefin under theinfluence of a free-radical catalyst, hoydrolyzing one of the methylgroups in a basic medium and acidifying, essentially as follows:

NaOH

Many methods exist for producing the salts of this invention from theacid. Initially, ammonia or ammonium hydroxide may be reacted with theacid to form the intermediate ammonium phosphonate. This in turn isreacted with, for example, a gold or copper compound, preferably in theform of its halide (e.g., auric chloride), to yield the final salt orthe metal complex when excess base is present.

More specifically the reaction between the ammonium phosphonate and themetal halide to form the salt is carried out, usually, at roomtemperature, or with moderate heating, using equimolar amounts ofreactants. The reaction, which usually is run in water, produces a solidproduct which may be isolated from the reaction medium by anyconventional means of separation.

For the most part, the metal phosphonates of this invention, as well asthe complexes thereof, appear to function as most conventional additivesdo. That is, it is believed that they undergo chemical decompositionduring use and that such decomposition products actually react with themetal of the surfaces being lubricated and form a film which reducesmechanical wear.

Several of the phosphonates of the present invention, however, do notdepend for their effectiveness of forming a film on the metal bychemical means. It has been observed that the gold complexes and thesilver and copper salts or their complexes, actually have their metalions reduced to the free metal, which in turn forms a very thin film ofsuch free metal on the surface being lubricated. The film thus depositedis a fixed, almost permanent solid lubricant. In other words, the solidfihns are formed, thereby permitting the surfaces of the lubricatedparts to move against each other with minimal wear, or no wear at all.Even if the solid film does wear, no substrate metal is lost (assumingsome film is always present) because it is not chemically involved inthe formation of the copper or gold film.

With respect to the gold, silver, and copper compounds, it is theorizedthat, since they deposit a coating of a solid that is softer than themetal substrate, this may provide improved lubrication by providing asofter, more yielding surface. However, no evidence has been found thatthis phenomenon of deposition is operative with the use of the otherphosphonates disclosed herein.

The gold, silver and copper compounds of this invention are initiallysoluble in the oil phase. Breakdown during lubrication begins thedeposition of the metallic solid upon the substrate metal of themechanism being lubricated. Thus, the gold, silver and copper compoundscan actually function two ways in keeping the sliding metal surfacesfrom wearing.

The phosphonates of this invention are preferably used in lubricatingoil compositions. These include mineral oils, both paraflinic andnaphthenic, and synthetic oils. These synthetic oils include syntheticester lubricating oils such as esters of 2,2-disubstituted,1,3-propanediol, trimethylolpropane, or pentaerythritol withmonocarboxylic acids having from 4 to about 25 carbon atoms. Thesynthetic oils also include polyolefin fluids, polysiloxane fluids,polyglycol ether fluids and polyphenyl ether and polyphenyl thioetherfluids. Suitable thickeners may be added to the liquid compositions toproduce greases or other thickened forms of lubricants. Other additives,such as antioxidants and detergents, may also be present, collectivelyor alternatively.

The basic nitrogen-containing compound useful in forming the complexesof this invention may be selected from a wide range of materials. Theyinclude primary, secondary, and tertiary alkyl amines, wherein the alkylgroup contains from 1 to about 30 carbon atoms, primary, secondary andtertiary aryl amines, the aryl group containing from 6 to about 30carbon atoms, the polyalkylene polyamines such as ethylene diamine,diethylene tn'amine, triethylene tetramine, tetracthylene pentamine,pentaethylene hexamine, nonaethylene decamine, and the like. Alsoincluded are heterocyclic amines, both cycloaliphatic and aromatic.

Illustrative of the alkylamines that may be used are the mono, di-, andtrimethylamines, the mono-, di-, and trihexylamines and the like. Themono-, di-, and triphenylamines illustrate aryl amines that one canemploy. Pyridine is a useful heterocyclic aromatic amine.

The following specific embodiments will serve to illustrate the practiceof this invention. It will be understood that no limitation on the scopeof the invention is intended by such illustrations.

EXAMPLE 1 About 45 g. (0.2 mole) of l-hexadecene and about 55 g. (0.5mole) of dimethyl phosphite were placed in a 250 ml. reaction flaskequipped with a stirrer, thermometer, reflux condenser, addition funnel,and a nitrogen inlet tube. The system Was flushed well with nitrogen;the reaction mixture was stirred and warmed to about 150 C.

About 2.0 g. of di-t-butylperoxide was added slowly to the reactionmixture over about hour. The heating and stirring were continued duringthe addition and for 1 /2 hours thereafter. The excess dimethylphosphite was removed by vacuum distillation. 69.5 (0.2 mole) ofdimethyl n-hexadecylphosphonate was recovered.

About 67 g. (0.2 mole) of the above dimethyl n-hexadecylphosphonate wasmixed with a solution of about 10 g. (0.25 mole) of sodium hydroxide inabout 150 ml. of methanol. The mixture Was stirred and warmed at refluxtemperature for about 3 hours. The mixture was allowed to cool to roomtemperature and about 0.25 mole of HCl as concentrated hydrochloric acidsolution was slowly added to the stirred mixture. This was followed bythe addition of 500 ml. of water. The product was recovered on a suctionfilter and washed twice, each time by stirring in a beaker with 500 ml.of water, then recovering by suction filtration. The crude product wasrecrystallized from a hexane-petroleum ether mixture to give the puremethyl n-hexadecylphosphonate.

About 9.6 g. (0.03 mole) of the above methyl n-hexadecylphosphonate wasmixed with a solution of 5 m1. ammonium hydroxide (28-30% sp. g. 0.9).About 3.9 g. (0.1 mole) HauCl 3H O was dissolved in 20 ml. of water andadded to the phosphonate solution. An excess of ammonium hydroxide wasadded and the mixture was extracted twice with diethyl ether. Thesolvent was removed from the ether extract by distillation. The solidproduct was washed twice by stirring with water and decanting. The lastof the water was removed from the product by azeotropic distillationwith benzene and finally removing the benzene. A phosphonate was formedin which the gold was Au+ and which was complexed with four parts ofammonia per part of gold phosphonate.

EXAMPLE 2 About 232 g. (0.75 mole) of l-docosene and about 247 g. (2.25moles) of dimethyl phosphite were placed in a 2 liter reaction flaskequipped with a stirrer, thermometer, reflux condenser (with a dryingtube attached to the outlet) and an addition funnel. The flask waspurged with nitrogen before adding the reagents. The mixture was stirredand warmed to about 150 C. While maintaining the temperature, about 3 g.of di-t-butylperoxide was added in small increments over about one hour.The temperature of the stirred mixture was maintained at about 150 C.for another 'hour after the peroxide addition was completed.

The mixture was allowed to cool and the apparatus was adapted for vacuumdistillation. The excess dimethyl phosphite was removed by distillationup to a pot temperature of about C. and an estimated pressure of 10-20mm. Hg. 311 g. of dimethyl n-docosylphosphonate was recovered.

About 300 g. (0.72 mole) of the above dimethyl ndocosylphosphonate wasmixed with a solution of about 40 g. (1 mole) of sodium hydroxide inabout 450 ml. of methanol. The mixture was stirred and warmed at refluxtemperature (about 68 C.) for about 3 /2 hours and then allowed to cool.While the temperature was kept between 45-50 C. (to keep the productliquid) 83 ml. of aqueous 37% hydrochloric acid solution and 400 ml.water was added to the mixture. This produced an unfilterable emul- 6EXAMPLE 5 sion at this stage. About 2 volumes of acetone were added 5and the product isolated on a suct1on filter. The product Similarly,additional complexes of gold phosphonates was recrystallized from asolution of benzene and petroleum ether. After drying 299 g. of methyln-docosylphosi f ifi i fi according to Example Analyses phonate wasobtained. in lcate e o owing structures:

A small amount (e.g. 0.2 mole, about 8.1 g.) of the 10 EXAMPLE 6 abovemethyl n-docosylphosphonate was dissolved in about 50 m1. of Warm 95%ethanol. An equivalent amount l of a water soluble salt of the desiredmetal [e.g., 0.1 mole CH Q-P ()--A .4NH Pb(NO .02 mole AgNO .01 moleCuCI etc.] was H mixed with the warm ethanol solution of the phosphonate22 a and warmed on a steam bath for 10-15 minutes. After cooling, thesolid product was isolated by filtration and EXAMPLE 7 purified bywashing and recrystallization. o

Alternately, the methyl n-docosylphosphonate was dis- 1 solved in anequivalent amount of ammonium hydroxide 0 'II solution, then reactedwith the metal ion. 0 E1 3 EVALUATION OF PRODUCTS The compounds ofExamples 3 to 7 were also tested The test used to obtain the data in thefollowing table in the Four-Ball Test described above. The phosphonatewas the well-known Shell Four-Ball Test. In this test, three 25 to betested was placed in a base grease prepared by addsteel balls of 52100steel are held in a ball cup. A fourth ing a modified clay thickener topolydecene fluid. The ball positioned on a rotatable vertical shaft isbrought into test was run for minutes at 200 F. under a 20 kg. contactwith the three balls and is rotated against them at load at '600 rpm.Following are illustrative results: a. predetermined load. The testlubricant is added to the ball cup, and at the end of the test, thesteel balls are 30 examined for wear scar. The size of the scar and rateof g gi wear, Wear wear per unit sliding distance represents theeffectiveness phosphoscar, rate, of the lubricant as an anti-wear agent.Example The data in the table below was obtained by placing a None 0.401016x101: metal methyl alkylphosphonate in n-hexadecane (except 21:23::1322 1288; where noted) and running the above noted test under the 7 7.5.356 .42x1oconditions shown.

Percent Wear Wear phospho- Temp., Load, Time, sear, rate, 00.] MetalPhosphonate nate F. kg. Rpm. min. mm. em. None None None 200 20 600 300.775 12.9X10- Cu" O p 1.31 200 20 600 30 .349 .38X10 Il/ CHsOP 1.51 20020 600 30 .302 .16Xl0- jiiiij.-ff?f.ii flflf 1. 53 200 20 600 30 .370.51X10-11 Pb+ do 1.52 200 20 600 30 .483 1.77x10- Au" O 0.475 200 20 60030 .368 .50X10' CHaO Cu al Au+ Same as above 0.475 300 20 600 30 .351.39X10- Copper phosphonates were prepared in a manner simi- We claim:lar to the procedure of Example 2. These, however, were 1. Lubricantcompositions comprismg a lubricating oil complexed withnitrogen-containing compounds, and or grease and an amount suflicient toimpart anti-wear analyses for carbon, hydrogen, phosphorus, nitrogen,and properties thereto of a compound of the formula metal contentindicated the following structures: 0

EXAMPLE 3 Rl 1 O O M. ZX H I Jn )q CH3OP-O-Cu-2NH;

I J wherein R is a hydrocarbyl group contammg from 14 to 022m 2 about 30carbon atoms, R' is a hydrocarbyl containing EXAMPLE 4 from 1 to about 6carbon atoms, X is selected from the group consisting of alkylamineshaving from 1 to about 30 carbon atoms, arylamines having from 6 toabout 30 CHaoPO ICu'NH2C2HNH' carbon atoms, ammonia and polyalkylenepolyamines, Z 2 1 5 is from 1 to 4, q is 1, M is a metal selected fromthe group 7 consisting of Group I-B, Group II-B and Group IV-A of thePeriodic Table and n is the valence of M, q being 1 and n being 3 when Mis gold.

2. The composition of claim 1 wherein the metal is selected from thegroup consisting of copper, silver, zinc, mercury and lead.

3. The composition of claim 1 wherein the metal is 1 old.

g 4. The composition of claim 1 wherein the metal is copper.

5. The composition of claim 1 wherein the metal is silver.

6. The composition of claim 1 wherein R is docosyl.

7. The composition of claim 1 wherein R is methyl.

-8. The composition of claim 1 wherein M is Cu, Z is 2, and X is NH 9.The composition of claim 1 wherein M is Au, Z is 2, and X is NH2C2H4NH2.

10. The composition of claim 1 wherein M is An, Z is 4, and X is NH 11.The com-position of claim 2 wherein R is docosyl and R is methyl.

12. The composition of claim 2 wherein R is hexadecyl and R is methyl.

13. The composition of claim 11 wherein the metal is gold.

14. The composition of claim 11 wherein the metal is copper.

15. The composition of claim 11 wherein the metal is silver.

References Cited UNITED STATES PATENTS 2,382,043 8/ 1945 Farrington etal 252-325 2,758,971 8/1956 Mikeska 25232.5 2,837,481 6/1958 Hotten eta1 25232.5

PATRICK P. GARVIN, Primary Examiner A. H. METZ, Assistant Examiner U.S.Cl. X.R. 260-430

